This invention relates to a method for cleaning reactors for the gas-phase processing of workpieces. In particular, the invention is directed to the in situ cleaning of reactors used for processing single disks.
It is customary to disassemble contaminated reactors, which are used for the gas-phase processing of workpieces, and to clean them by wet chemical means. This represents a considerable expense, particularly in the case of reactors, which are constructed as vacuum vessels. For this reason, so-called in situ solutions have been provided, which permit a reactor to be cleaned without being disassembled. For this purpose, a suitable gas mixture is introduced through existing gas inlets. Under the conditions existing in the reactor, this gas mixture causes the contaminated reactor parts to be cleaned by an etching process. This method is customary particularly with reactors used to carry out plasma-aided CVD (chemical deposition from the vapor phase) processes.
The gas inlet systems, which during the deposition process are used to supply the gaseous starting materials (process gas) for the layer that is to be deposited, are charged with an etching gas such as CF.sub.4 /O.sub.2 or NF.sub.3 during the in situ cleaning step. The cleaning of the interior parts of the reactor by etching is carried out under the action of an HF plasma and an elevated temperature in the reactor.
It is a disadvantage of this method that the gas paths, used to introduce and exhaust the etching gas, are the same as those used to realize the processing of the substrate. They are designed so that the effect of the substrate processing takes place as far as possible only at the surface of the substrate and not anywhere else in the reactor (for example, the gas nozzle above the substrate).
However, it may be noted that the so-called dead spaces of the reactor, through which the process gas does not flow and which are not flushed, are contaminated most quickly. For this reason, only a limited cleaning effect can be attained by the above described conventional method of in situ cleaning or the etching process must be carried out for a disproportionally long time. The optimization of the process gas paths through the reactor to achieve the optimum processing effect on the surface of the substrate is in conflict with the requirements of the optimum processing effect at the reactor walls during the step of in situ cleaning by etching.
It is an object of the invention to reduce the effort involved in cleaning reactors for the gas-phase processing of work pieces.